This invention generally relates to transducers and, more particular to an electrostatic pressure transducer.
A transducer is an electronic device that converts energy from one form to another. Typically, a transducer may include a diaphragm which moves or vibrates in response to a some form of energy, such as sound. Some common examples of transducers with diaphragms are microphones, loudspeakers, thermometers, position and pressure sensors.
One of the problems with prior pressure transducers is with their sensitivity. Often these pressure transducers can not detect small changes in pressure.
A pressure transducer system in accordance with one embodiment of the present invention includes a housing with a chamber, a member with a stored electrical charge, and a pair of electrodes that are at least partially in alignment with each other. At least a portion of the chamber is at a reference pressure. The member is connected to the housing and extends across at least a portion of the chamber. Each of the pair of electrodes is spaced from and on substantially opposing sides of the member. The member is movable with respect to the pair of electrodes or one of the pair of electrodes is movable with respect to the member in response to a monitored pressure.
A method for making a pressure transducer system in accordance with another embodiment of the present invention includes providing a housing with a chamber. At least a portion of the chamber is at a reference pressure. A member with a stored electrical charge is provided. The member is connected to the housing and extends across at least a portion of the chamber. A pair of electrodes is provided. Each of the pair of electrodes is connected to the housing and is spaced from and on substantially opposing sides of the member. The member is movable with respect to the pair of electrodes or one of the pair of electrodes is movable with respect to the member in response to a change in pressure.
A method for measuring pressure in accordance with another embodiment of the present invention includes exposing a member with a stored electrical charge or one of a pair of electrodes to a pressure to be measured. The member is connected to a housing with a chamber and extends across at least a portion of the chamber. Each of the pair of electrodes is spaced from and on substantially opposing sides of the member. The member is moved with respect to the pair of electrodes or one of the pair of electrodes is moved with respect to the member in response to a monitored pressure. The movement of the member or one of the pair of electrodes is measured and the pressure is determined based on the measured movement.
The present invention uses embedded electrical charge trapped at the interface of dissimilar insulators. The electronic charge density of the present invention can be three to four orders of magnitude greater than that of known electret materials. Thus, the present invention has a significant advantage in sensitivity. Furthermore the size of pressure transducers based on the present invention can be made very much smaller than pressure transducers using electrets, and yet have comparable or greater sensitivity. Hence, such pressure transducers can be designed as MEMS devices.
The present invention provides a pressure transducer which is extremely sensitive to slight changes in pressure. With the present invention, a change of position of a member or one of the pair of electrodes of less than one nanometer can be detected. The present invention is useful for detecting static, quasi-static, and dynamic changes in pressure and can be used to detect such pressure changes in gasses, liquids, or solids when used as a weighing scale.